The immune system of vertebrates (for example, primates, which include humans, apes, monkeys, etc.) consists of a number of organs and cell types which have evolved to: accurately and specifically recognize foreign microorganisms (“antigen”) which invade the vertebrate-host; specifically bind to such foreign microorganisms; and, eliminate/destroy such foreign microorganisms. Lymphocytes, as well as other types of cells, are critical to the immune system and to the elimination and destruction of foreign microorganisms. Lymphocytes are produced in the thymus, spleen and bone marrow (adult) and represent about 30% of the total white blood cells present in the circulatory system of humans (adult). There are two major sub-populations of lymphocytes: T cells and B cells. T cells are responsible for cell mediated immunity, while B cells are responsible for antibody production (humoral immunity). However, T cells and B cells can be considered interdependent—in a typical immune response, T cells are activated when the T cell receptor binds to fragments of an antigen that are bound to major histocompatability complex (“MHC”) glycoproteins on the surface of an antigen presenting cell; such activation causes release of biological mediators (“interleukins” or “cytokines”) which, in essence, stimulate B cells to differentiate and produce antibody (“immunoglobulins”) against the antigen.
Each B cell within the host expresses a different antibody on its surface—thus one B cell will express antibody specific for one antigen, while another B cell will express antibody specific for a different antigen. Accordingly, B cells are quite diverse, and this diversity is critical to the immune system. In humans, each B cell can produce an enormous number of antibody molecules (i.e., about 107 to 108). Such antibody production most typically ceases (or substantially decreases) when the foreign antigen has been neutralized. Occasionally, however, proliferation of a particular B cell will continue unabated; such proliferation can result in a cancer referred to as “B cell lymphoma.”
Non-Hodgkin's lymphoma is one type of lymphoma that is characterized by the malignant growth of B lymphocytes. According to the American Cancer Society, an estimated 54,000 new cases will be diagnosed, 65% of which will be classified as intermediate- or high-grade lymphoma. Patients diagnosed with intermediate-grade lymphoma have an average survival rate of two to five years, and patients diagnosed with high-grade lymphoma survive an average of six months to two years after diagnosis.
Conventional therapies have included chemotherapy and radiation, possibly accompanied by either autologous or allogeneic bone marrow or stem cell transplantation if a suitable donor is available, and if the bone marrow contains too many tumor cells upon harvesting. While patients often respond to conventional therapies, they usually relapse within several months.
A relatively new approach to treating non-Hodgkin's lymphoma has been to treat patients with a monoclonal antibody directed to a protein on the surface of cancerous B cells. The antibody may be conjugated to a toxin or radiolabel thereby affecting cell death after binding. Alternatively, an antibody may be engineered with human constant regions such that human antibody effector mechanisms are generated upon antibody binding which result in apoptosis or death of the cell.
Rituximab® (IDEC Pharmaceuticals Corporation) is one of a new generation of monoclonal antibodies developed for the treatment of B cell lymphomas, and in particular, non-Hodgkin's lymphoma. Rituximab® is a genetically engineered anti-CD20 monoclonal antibody with murine light- and heavy-chain variable regions and human gamma I heavy-chain and kappa light-chain constant regions. Rituximab® is more effective than its murine parent in fixing complement and mediating ADCC, and it mediates CDC in the presence of human complement. The antibody inhibits cell growth in the B-cell lines FL-18, Ramos, and Raji, sensitizes chemoresistant human lymphoma cell lines to diphtheria toxin, ricin, CDDP, doxorubicin, and etoposide, and induces apoptosis in the DHL-4 human B-cell lymphoma line in a dose-dependent manner.
However, many patients are refractory to or relapse following Rituximab® therapy, as well as chemotherapy. Therefor, there still remains a need for lymphoma treatments which may be combined with Rituximab® therapy or chemotherapy in order to increase the chance of remission and decrease the rate of relapse in lymphoma patients.
Many groups have suggested using cytokines for the treatment of various types of cancers. For instance, Wang et al. suggested that cytokines are “directly cytotoxic to tumor cells” and showed that interleukin-1 alpha (IL1α) potentiated the anti-tumor effect of anti-tumor drugs against several human tumor cells in vitro (Int. J. Cancer (Nov. 27, 1996) 68(5): 583-587). Bonvida et al. disclose that cytokines have the potential to “enhance the efficacy of chemotherapeutic agents” and show that recombinant tumor necrosis factor and the chemotherapeutic agent cisplatin show a synergistic effect against ovarian cancer cells (Gynecol. Oncol. (September 1990) 38(3): 333-339). U.S. Pat. No. 5,716,612 teaches that IL-4 may be used to potentiate the effect of chemotherapeutic agents in the treatment of cancer.
However, some groups have also recognized that cytokines may play a detrimental role in the development of some cancers. For instance, interleukin-6 (IL6) has been known for the ability in some instances to inhibit apoptosis of leukemic cells. (See Yonish-Rouach et al. Wild type p53 induces apoptosis of myeloid leukemic cells and is inhibited by interleukin-6. Nature 352: 345-347 (1991)). Recently it was shown that IL6 may play a role in the resistance of some leukemic cells to anti-cancer chemotherapeutic agents, and that, in vitro, anti-IL6 antibody increases the sensitivity of cisplatin-resistance K562 cells to cisplatin-induced apoptosis. (See Dedoussis et al. Endogenous interleukin 6 conveys resistance to cis-diamminedichloroplatinum-mediated apoptosis of the K562 human leukemic cell line).
A potentiating effect on B cells has also been postulated for IL10, the production of which has been reported to be upregulated in some cell lines derived from B cell lymphomas (See Cortes et al. Interleukin-10 in non-Hodgkin's lymphoma. Leuk Lymphoma 26(3-4): 251-259 (July, 1997). However, when the serum of NHL patients was tested for correlation between IL10 levels and prognosis, more significance was placed on the levels of viral IL10, which is produced from a homologous open reading frame BCFR1, located in the genome of the Epstein Barr Virus (EBV). In fact, another group reported at about the same time that IL10 was an autocrine growth factor for EBV-infected lymphoma cells. (See Beatty et al. Involvement of IL10 in the autonomous growth of EBV-transformed B cell lines. J. Immunol. 158(9): 4045-51 (May 1, 1997)). Alternatively, others have hypothesized that IL6 and IL10 production by macrophages plays a key role in the occurrence of lymphocytic diseases. (See U.S. Pat. No. 5,639,600).
It has also been reported that IL10 may work in combination with IL6, IL2 and TNF-alpha to increase proliferation of non-Hodgkin's lymphoma cells. (See Voorzanger et al. Interleukin-(IL)10 and IL6 are produced in vivo by non-Hodgkin's lymphoma cells and act as cooperative growth factors. Cancer Res. 56(23): 5499-505 (Dec. 1, 1996). Also statistically significantly higher levels of IL2, IL6, IL8, IL10, soluble IL2 receptor, soluble transferrin receptor and neopterin were observed in NHL patients as compared to a control group, although no single parameter was found to be of prognostic significance. (See Stasi et al. Clinical implications of cytokine and soluble receptor measurements in patients with newly diagnosed non-Hodgkin's lymphoma. Eur. J. Haemotol. 54(1): 9-17 (January, 1995).
However, there have been just as many reports in the literature which have suggested that cytokines such as IL10 show no correlation to disease progression, and that such cytokines may actually be helpful in combating lymphoma rather than contributing to the disease. For instance, when Bonnefoix et al. tested the potential of ten cytokines (IL2, IL3, IL4, IL6, IL10, IL13, G-CSF, GM-CSF, interferon alpha and interferon gamma) to modulate the spontaneous proliferative response of B-non-Hodgkin's lymphoma cells of various histological subtypes, this group found that each cytokine could be either inhibitory or stimulatory depending on the sample, and that there was no relationship with different histological subtypes. In fact, U.S. Pat. No. 5,770,190, herein incorporated by reference, suggests administration of IL10 in conjunction with chemotherapeutic agents as a treatment for acute leukemia.
It would be a benefit to lymphoma patients if therapeutic regimens incorporating anti-cytokine antibodies could be devised whereby such antibodies could be used to increase the sensitivity of B lymphoma cells to other types of therapeutic drugs. It would be particularly helpful if anti-cytokine antibodies could be administered for the purpose of avoiding or overcoming the resistance of B lymphoma cells in lymphoma patients to chemotherapeutic agents, and for the purpose of potentiating the apoptotic activity of therapeutic antibodies. Such combined treatment regimens would add to the therapies available to lymphoma patients and potentially decrease the rate of relapse in these patients.